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I enjoy using squashfs for compression because of the simplicity of mounting them as loop devices to access the files inside.

I have a lot of rar, tgz and zip files that I would like to convert to squashfs.

In this answer, I saw that it is possible to use a pseudo file when compressing a disk image to squashfs to avoid having to use a temporary file the size of the whole disk.

mkdir empty-dir
mksquashfs empty-dir squash.img -p 'sda_backup.img f 444 root root dd if=/dev/sda bs=4M'

I would like to use pseudo files to convert from rar, tgz or zip to squashfs in the same way (on the fly), so I don't have to first extract the whole archive to disk and then compress to squashfs in a separate operation.

Some of these archives contain thousands of individual files, some of which will have spaces or other special characters in their filenames.

I looked at the README, and I think I would need to use the -pf <pseudo-file> option, but I'm not sure how to create the pseudo file on the fly (and also not have problems with filenames with spaces). I think I would need to use process substitution to create the list of files from the source archive.

Ideally I would like to have a command that is able to convert any rar, tgz or zip without having to individually create the pseudo file for each archive, but if anyone can tell me how I can do it with one of those archive formats, then hopefully I can work it out for the others.

Thanks everyone.

2 Answers 2

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You could mount them with fuse-zip or archivemount and then create the squashfs file from the mount point.

For example, this would work for a zip file:

$ mkdir /tmp/zmnt
$ fuse-zip -r /path/to/file1.zip /tmp/zmnt
$ mksquashfs /tmp/zmnt /path/to/file1.squashfs
$ fusermount -u /tmp/zmnt
0

There is tar2sqfs from https://github.com/AgentD/squashfs-tools-ng/

Might at least be an alternative worth investigating.

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